Process fired heaters are collectively the major source of refinery carbon dioxide emissions. In a typical U.S. refinery, for example, approximately seventy percent (70%) of the carbon dioxide emitted to the atmosphere originates from process fired heaters.
These fired heaters combust natural gas, refinery fuel gas or liquid fuel oil with air and as a result emit a flue gas which is relatively dilute (15 V % or less) in CO2 with nitrogen present as the primary gas. Although technology exists for capturing the dilute CO2 from this stream, it is highly capital intensive and not practiced commercially. Another method involves feeding of purified oxygen from an air separation plant to the fired heaters which significantly increases the CO2 concentration in the fired heater flue gas to the point where near pure CO2 can be recovered after removal of sulfur species, particulates and water. However, this configuration also requires a recycle of CO2 to the furnace to moderate the resulting temperature and also results in high investment and operating costs primarily related to the air separation plant and is not economically practical. Further, separate CO2 capture facilities may be needed for each fired heater.
As a result of the need for an efficient and economical technique for reducing the CO2 emissions in a refinery, applicant's herein disclose a novel process to eliminate the need for post combustion CO2 capture from fired heaters (at atmospheric pressure and in dilute phase) in a petroleum refinery by capturing CO2 in a centralized facility and providing fuel gas low in carbon to the process fired heaters.